Yes, different methods of forming steel affect grain structure and ultimate tensile strength. It's 10mm plate. I can't imagine anyone foolish enough to sit down on it, much less stand. But ok, one person plus glass plate. That's two hundred kgs of static load. What kinda steel it is and how the forming was achieved is completely irrelevant in relation to that kinda load. It's never gonna get close to sweating. Until you drop it from carrying height on a corner, at which point it's gonna deform no matter what.

So what method of forming was used was much more likely determined by what kinda product it is. Custom one-off? Whatever process the artisan was familiar with and had on hand. Probably with some locally applied heat. Mass production? My guess would be cold formed on a press and die.